Listen very carefully to Donnyman and others who are cautioning you on building/flying and altering the Spit.

On building most kits are not true to scale. They have been altered by the manufacturer/designer to give the best characteristics for the size and weight of the model. Do not modify unless you know exactly what the modifications will do to the flying characteristics. Even adding detail can soon put the model over weight and make it difficult to fly. This is your first warbird build it to plans.

On flying I think this may be a bit early for your abilities. A balsa plane will not take the rough handling that a foamy will.
One good ground loop or nose over will probably result in major repairs. A hard landing will remove the retracts/landing gear faster than you can say ooooppssss. Hard landings often result in bouncing back into the air at low speed and a stall and dropped wing resulting in a roll over into the ground. Any warbird is less forgiving you should fly a low wing tail dragger trainer until you can land it with confidence every time.

If the plane is a good flyer why alter anything after all its your first one of this type. Why add to the frustration if your alterations may not improve performance.

Dennis